Tidal Capture of Stars by Intermediate-Mass Black Holes

Abstract

Recent X-ray observations and theoretical modelling have made it plausible that some ultraluminous X-ray sources (ULX) are powered by intermediate-mass black holes (IMBHs). N-body simulations have also shown that runaway merging of stars in dense star clusters is a way to form IMBHs. In the present paper we have performed N-body simulations of young clusters such as MGG-11 of M82 in which IMBHs form through runaway merging. We took into account the effect of tidal heating of stars by the IMBH to study the tidal capture and disruption of stars by IMBHs. Our results show that the IMBHs have a high chance of capturing stars through tidal heating within a few core relaxation times and we find that 1/3 of all runs contain a ULX within the age limits of MGG-11, a result consistent with the fact that a ULX is found in this galaxy. Our results strengthen the case for some ULX being powered by intermediate-mass black holes.